The present invention relates to a gas laser device, and articularly relates to a gas laser device including a dust filter or eliminating dust generated in a laser chamber.
A dust filter for eliminating dust generated inside a laser chamber in a laser device such as an excimer laser device and a fluorine laser device is conventionally known and is disclosed in, for example, Japanese Patent Laid-open No. 6-132582. FIG. 10 shows a configuration of a section in a side view of an excimer laser device 101 disclosed in Japanese Patent Laid-open No. 6-132582, and FIG. 11 shows a section taken along the line 11xe2x80x9411 in FIG. 10. FIG. 11 is illustrated so that the vertical direction is reversed.
In FIG. 10 and FIG. 11, an excimer laser device 101 includes a laser chamber 102 containing laser gas being a laser medium. A pair of discharge electrodes 105 and 105 for causing discharge to happen to excite laser gas and oscillating laser light are disposed to face to each other inside the laser chamber 102. Further, inside the laser chamber 102, a flow-through fan 121 for circulating the laser gas inside the laser chamber 102 to send it to an area between the discharge electrodes 105 and 105, and a heat exchanger 103 for cooling the laser gas heated between the discharge electrodes 105 and 105 are respectively placed at predetermined positions.
Window holders 110 and 110 are provided at both front and rear end portions of the laser chamber 102. A front and rear windows 107 and 109 for transmitting the laser light are respectively fixed at tip end portions of the window holders 110 and 110. Labyrinths 111 and Ill are placed between the laser chamber 102, and the windows 107 and 109.
Inside the laser chamber 102, the discharge electrodes 105 and 105 arc worn by discharge, and very small metal powder, halogenide thereof and the like are generated. The excimer laser device 101 includes a dust filter 112 for eliminating the dust. A filter case 114 including filter elements 113 and 113 therein is connected to an outer wall 102B of the laser chamber 102. The laser chamber 102 and the filter case 114 arc communicated with each other via a filter inlet port 115 provided at approximately a center portion in a longitudinal direction of the discharge electrodes 105 and 105 and a filter outlet port 116 provided at both end portions of the laser chamber 102.
A flow line of the laser gas which is circulated inside the laser chamber 102 by the flow-through fan 121 driven by a motor 120 is shown by the arrows G in FIG. 10 and FIG. 11. Part of the laser gas G circulated by the flow-through fan 121 is drawn from the filter inlet port 115 into the filter case 114, as shown by the arrow G1, and separates into a left and right side to pass through the filter elements 113. Thereby, the dust mixed in the laser gas G1 is caught by the filter elements 113 and 113. The laser gas G1 having the dust eliminated to be clean is discharged to the insides of the window holders 110 and 110 and passes through the labyrinths 111 to return into the laser chamber 102.
As shown in FIG. 10, the filter inlet port 115 is provided at a corner of an inner wall 102A of the laser chamber 102, and forms a receiving port like a funnel relative to the laser gas G. Thereby, the laser gas G1 is passed into the filter case 113 from the filter inlet port 115 as much as possible and thereby the amount of the dust caught is increased.
However, the prior art disclosed in Japanese Patent Laid-open No. 6-132582 has the disadvantages described below.
Specifically, in the prior art, as shown in FIG. 10, the filter inlet port 115 forms the receiving port like a funnel. The flow of the laser gas G passing near the filter inlet port 115 and flowing into between the discharge electrodes 105 and 105 is disturbed by the receiving port. In addition, since the filter inlet port 115 is provided only at approximately the center portion in the longitudinal direction of the discharge electrodes 105 and 105 as shown in FIG. 11, such disturbance selectively occurs at approximately the center portion in the longitudinal direction of the discharge electrodes 105 and 105. As a result, at approximately the center portion of the longitudinal direction of the discharge electrodes 105 and 105, the average flow rate sometimes reduces to be lower than at the other points. Such reduction of the flow rate sometimes occurs as a variation with time, and the phenomenon in which the flow rate suddenly reduces and thereafter returns to the original value sometimes happens.
When there is ununiformity in the flow rate distribution of the laser gas G between the discharge electrodes 105 and 105 in the longitudinal direction of the discharge electrodes 105 and 105, discharge is disturbed and becomes unstable at the points at which the flow rate is slow, thus causing the disadvantages that the power of the laser light is reduced and no more energy can be inputted. If the flow rate of the laser gas G is varied with time, when the flow rate is low as described above, the power of the laser light is reduced and the variation of the power with time is increased.
The present invention is made to eliminate the above disadvantages of the prior art, and its object is to provide a gas laser device in which a flow rate of laser gas flowing between discharge electrodes is approximately uniform in a longitudinal direction of the discharge electrodes without a variation with time.
In order to attain the above object, a gas laser device according to the present invention includes
a laser chamber containing laser gas;
a pair of discharge electrodes disposed inside the laser chamber to face to each other for exciting a laser medium by discharge to thereby oscillate laser light,
a fan for circulating the laser gas to send the same to an area between the discharge electrodes, and
a dust filter for eliminating dust generated inside the laser chamber; and has a configuration
in which a filter inlet port, which is formed in an inner wall of the laser chamber and guides the laser gas into the dust filter, is formed to be approximately vertical to a flow line of the laser gas flowing inside the laser chamber.
According to the above configuration, the filter inlet port seldom disturbs the flow of the laser gas flowing inside the laser chamber. Accordingly, the flow rate of the laser gas in the longitudinal direction of the discharge electrodes is seldom lowered at a specific point or seldom varied by being influence by the filter inlet portion. Thereby, it becomes possible to obtain the flow of the laser gas with the flow rate being always fixed and stable, and thus the discharge becomes stable and the output of the laser light also becomes stable.
Further, a gas laser device may include
a laser chamber containing a laser medium,
a pair of discharge electrodes disposed inside the laser chamber to face to each other for exciting the laser medium by discharge to thereby oscillate laser light,
a fan for circulating laser gas to send the same to an area between the discharge electrodes, and
a dust filter for eliminating dust generated inside the laser chamber; and may have the configuration in which
a filter inlet port, which is formed in an inner wall of the laser chamber and guides the laser gas into the dust filter, is formed over approximately an entire area in a longitudinal direction of the discharge electrodes.
According to the above configuration, the filter inlet port has approximately uniform influence on the flow rate distribution of the laser gas over the entire area in the longitudinal direction of the discharge electrodes. Accordingly, the flow rate of the laser gas in the longitudinal direction of the discharge electrodes seldom is reduced at a specific point or varied by the influence of the filter inlet port.
Furthermore, a gas laser device may include
a laser chamber containing a laser medium,
discharge electrodes disposed inside the laser chamber to face to each other for exciting the laser medium by discharge to thereby oscillate laser light,
a fan for circulating laser gas to send the same to an area between the discharge electrodes,
a dust filter for eliminating dust generated inside the laser chamber, and
a guide vane with an inlet port thereof being placed at a fan discharge portion of the fan over approximately an entire area in a longitudinal direction of the discharge electrodes, which guides the laser gas discharged from the fan into a filter inlet port of the dust filter formed in an inner wall of the laser chamber.
According to the above configuration, the laser gas discharged from the fan is uniformly drawn into the inlet port of the guide vane over approximately the entire area in the longitudinal direction of the discharge electrodes. Thereby, the influence exerted on the laser gas by the filter inlet port becomes approximately uniform relative to the longitudinal direction of the discharge electrodes, and thus the flow rate of the laser gas seldom reduces at a specific point or varies.